Sail



Feb. V17, 1931. H, H, PLATT 1,793,373

SAIL

Filed Aug. v274. 1928 Patented Feb. 17, 1,931V y HAVILAND Yrryrrai'rr, or wanprncnonn, PENNSYLVANIA- .i Application filed August 27,

This invention relates to improvements l wind propelled boats, and relates lmore'particularly to improvements in the sails constituting an essential part thereof. v

The principal object ofthe invention is to provide a sail of novel form which shall be generally more ecient than the sails of the prior practice. r n Y The invention also resides in certain novell and advantageous structural features herein after set forth and illustrated in the attached drawings, in which:

Figure lis a side elevational view of a boat equipped with a sail made in accordance with my invention;

Fig. 2 is a front elevational view of the boat; Y

Fig. 3 is atransverse section on the line 3 3, Fig. l, and

Fig. 4 is a diagram illustrating the operating characteristics.

VlfVith reference to the drawings, the sailV l vin a preferredrform consists of a hollow framework which in side elevation-may conform proportionally to any of the accepted sail shapesand which in horizontal cross section takes the form of an efficient airfoil section, suoli for example as that knownas Got,- tingen A10. This horizontal sectional form preferably is maintained consistently from/ top to bottom of the sail.V This framework is covered with sail cloth or other suitable material which constitutes the effective sail surfaceV and which preferably isi drawn tightly over the framework so that itconforms closely to the outline of the latter.

In one embodiment of thisfsail, the frame i work may consist of a plurality of substan 46 A tially flat frames 2, see Fig. 3, corresponding superimposed relation, and each is connected with the adjacent frame or frames by flexible' means of such length that when the framework is extended a sail of desired surface area isobtained. Obviously, the covering material A lsail Vconstructed on y lined' ab'oveqhas certain. material` advantages over the `forms `ofsail now commonly em- 1928. serial NQ. 302,223.

itself may constitute the flexible connecting means. 'Thesai-l-so constructed is' collapsible Y vertically, the individual horizontal frame plecescollapsing one upon the other as the sail `is released from the top. This permits' reefjy ing ofthe sail in the usual manner. f

,Y As shown, a passage is provided through the frames for the mast il, which thus extends through the .interior of the .sail .andf isA entirely surroundedand embracedtherebyj eX- cept in those portions which project atlthe top and'bottoml of the framestructure. v The-mast shou'ldbe located in advance offorclose'r to the yleading edge `of the' sail than the center of pressure which, in theVv particular airfoil section Gttingen 410 lies from the leading edge a distance equal approximatelyjto 25%'wof the length of thefoili' f' Y -1 'The flat frames 2 which make up ythe framework asa whole lare so relatively arranged as to preserve the predetermined Yrelation between mast position and center'of pressure.'

rThe sail may be elevated and lowered on the mast .by means `,of the -usua-lftackle attached to the'mast and to thetop Vof the sail struc-r ture. 'Preferably the lowermost frame of the' structure is tion: as la boom'.

rlered- The arodyliemj@ fncy Ofimy sail is Yconsiderably `greater than that ofsails of therusual form, whichfor anyV given sailY area gives an increased propulsive force and aifords better speed sailing into the wind.

made sufficiently heavy to func- Y the vprinciple l dut- I l A sail constructed in accordan'cewith Ymy in-r 1 ventionalso `possessesthe characteristic of developing maximumeiiic'iency at a relatively low Vangle lof attack, which'permits sailingl closer into the wind. YMy sail also reduces the capsizing'force 'of the wind, permitting a larger sail area. or greater safety wlth a given area than canbe obtained with sails j-of the vusual design. The'general efficiency 1s also increased, in that the sail 'substantiallyl en-V clos'es and thereby eliminatesthe air resistaY graphic comparison `of theaction of the Qrdinary sail with a sail made in accordance with my invention. Assuming a lift force of the value shown, it will be apparent that the Y drag force for my sail (designated by line D) will be less than the drag (D) for a sail of the usual form, the relative lengths of Dand Y D as Vshown being approximately :proportionate tothe actual values taken from wind tunnel data. Combining the forces for V.the respective sails gives Jfor my sail an effective `propulsive component P,y and for the other" sail a very considerably small component P',l new sail will be ap` The advantage of the parent.

I claim:

1X1; In'asail boat,a'.lmast,andasubstantially4 rigid sail osymmetrical section substantially surrounding said mast.

.2. Ina sail boat, a mast, and a sail substantially surrounding said mast, said saily being of symmetrical section and conforming throughoutits horizontal cross section to an airfoil section of predetermined eiliciency.

.-3. A sail comprising a plurality of flatY symmetrical frames each having throughout substantially the airline of an airfoil section and connected in spaced relation vertically,

` and a fabric cover for the framework formed by said sections, saidV framework `being of sufficient widthto permit the passage through tlie interior of a mast uponwhich the sail mayV be supported;

4. A sail comprising a hollow structure oit symmetricalf section and vconrorming f- 'throughout itslcross sectional form substan- Y,

tially to an airfoill section. y Y

5. A hollow sail comprising a supporting frame of symmetrical section, and a cover therefor, said frame being adaptedto maintainthe cover throughout the horizontal secy tion in the `form of an eilicient airfoil section.

6. In a boat,a mast, and a sail completely V surrounding the mast,*s'aid sail being of sym-V f vmetrical section and being held transversely and with vsubstantial yrigidityin the form of z an eiicient airfoil section. f f Y f HAVILAND I-I. PLATT. 

